A single-stage evaporator system is used to concentrate 10,000 kg/h of a NaOH solution from 10% to 45%. The feed is heated up using the residual heat from the condensed steam before entering the evaporator.

The concentrated solution is cooled down using water in a second heat exchanger. The hot utility is a saturated steam at 3.5 atm, which condenses at the evaporator and exits the heat exchanger at 35C.

The evaporation chamber is maintained at 150 mmHg vacuum with respect to 760 mmHg. The NaOH solution is fed to the system at 20C and to the evaporator at 45C. A cooling water flowrate of 15,728 kg/h is used to cool down the concentrated solution, enters at 20C, and leaves at 30C.

The global heat transfer coefficient is 1500 kcal/(m2 hC). Determine:

a. Solution boiling point.

b. Evaporator area.

c. Area of the heat exchangers. The global heat transfer coefficients are 650 and 125 kcal/(m2 hC) for the feed heated and the solution cooler, respectively.